This invention relates to key data entry systems for use in electronic apparatus such as electronic musical instruments.
Electronic keyboard musical instruments such as electronic organs include those in which the accompaniment sound is produced automatically or semi-automatically as the player is performing the melody part of a piece of music so that even beginners can attain the performance of the combination of melody and accompaniment of a musical piece with easy and simple keyboard operation. In some of such musical instruments, chord performance can be obtained by operating performance keys with a single finger. In such musical instruments however, erroneous entry of key data is possible due to key chattering occurring at the time of depressing and releasing keys. To prevent this erroneous entry of signals, it has been proposed to let a key depression signal to be entered immediately when a key is depressed and let a key release signal to be entered a predetermined period of time after the key is released.
In this case, however, extreme inconvenience arises when a certain key is released simultaneously with the depression of a different key. At such a time, it is possible that both the keys are detected to be simultaneously operated, thus causing two different chords to be produced momentarily.
In addition, with such a key data entry system it is difficult to let a chord be specified with the operation of a plurality of keys and let the operated keys be memorized in a memory circuit because strictly speaking the individual keys as the chord specification keys are actually operated at different timings although these keys are apparently operated together. Therefore, it is likely that a chord which is not intended by the operator or player would be produced according to the content of the memory circuit.